The NFL and NFL Players Association will stage an important negotiating session Wednesday in Washington, D.C., to continue their work toward an agreement on implement testing for human growth hormone, according to a source apprised of the meeting.

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Among those in attendance will be NFLPA associate general counsel Heather McPhee and NFL senior vice president of law and labor policy Adolpho Birch, as well as lawyers from both sides. The session is considered a critical one, as the hope is to have testing in place for the 2013 season.

Earlier this week, a source characterized the sides as "much further along" than they have been at any point since the NFL and NFLPA agreed to work toward HGH testing in 2011, when the collective bargaining agreement was signed.

There are three categories of key issues that need to be ironed out before a deal on testing can be finalized: procedural, economic and due process/appeals. Among key procedural questions: How often will the players be tested, how will the samples be taken, how will they be stored, as well as destroyed? Also, the chain of custody for the samples must be determined.

Each HGH testing kit costs $2,200, so it needs to be discussed who will foot the bill.

Finally, the sides must agree on due process and appeals. If a player tests positive for HGH, what is his right to appeal, and how does it tie into the broader NFL drug policy? The arbitration process also needs to be discussed. The NFL is pushing for retroactive discipline dating to the initial blood draw (one sample would be taken for the population study, another for testing). Players have been told that if someone tests especially high for HGH, that player would be put on a watch list and tested again at a later time to check if his levels changed or remained consistent with the original test.

Confidentiality also is a point of discussion. The blood samples will be identified by numbers, with each series of numbers corresponding to a player name. It must be determined who has access to those results.

Some players feel blind-sided by these tests, but HGH typically leaves the body in 48 hours, so the players will have plenty of notice before the first round of testing.

An email from the union to players, obtained earlier in the week, said both sides jointly had hired a doctor to conduct a study on players to determine the threshold for a positive HGH test. The email said the blood samples will be used solely for the study. Every player will have his blood drawn and compared against a control group of former players who have been tested.

A separate memo sent Monday from the NFLPA to the players said: "In preparation for training camp, you should be prepared to provide a sample of blood for your routine and required training camp physical." Those samples can't be tested for HGH until after the issues are finalized and agreed upon.